Male breast cancer, which makes up approximately 1% of all breast
cancers, is an aggressive disease with poor prognosis. We investigated the effects of dietary supplementation with
selenium in the form of
methylseleninic acid [(MSeA) 2.5 mg
selenium/kg] on mammary
tumorigenesis in male MMTV-PyMT mice. The mammary
tumor latency was 14.6 weeks for the MSeA-fed group and 13.8 weeks for the controls fed the AIN93G diet (p < 0.05). Dietary supplementation with MSeA, versus the control, resulted in a 72% reduction in
tumor progression, a 46% reduction in both final volume and weight of mammary
tumors, and a 70% reduction in the number of lung
metastases. Mammary
tumorigenesis in MMTV-PyMT mice, versus non-
tumor-bearing wild-type mice, resulted in significant increases in concentrations of
plasminogen activator inhibitor-1,
urokinase plasminogen activator,
monocyte chemotactic protein-1, and
vascular endothelial growth factor, but not
aromatase and
estrogen, in the plasma. Concentrations of all variables mentioned above in both plasma and mammary
tumors were lower in MSeA-fed mice. Mammary
tumorigenesis reduced plasma levels of
adiponectin compared to non-
tumor-bearing controls.
Adiponectin concentrations in mammary
tumors, but not in plasma, were higher in MSeA-fed mice than in controls. In summary, dietary supplementation with
selenium in the form of MSeA inhibits mammary
tumorigenesis and its pulmonary
metastasis in male MMTV-PyMT mice.